Who lives in cryoconite holes?

Not hobbits, that’s for sure. In fact, a cryoconite hole is about as far from a hobbit hole as you can imagine.

Hobbit hole

Cryoconite hole

Found in Middle Earth

Found at the ends of the earth

Not nasty, dirty, or wet

Definitely nasty, dirty, and wet

Comfortable

Cold

Full pantry

Very low nutrient environment

Round front door with brass knob

Round ice lid that sometimes melts

Residents typically do not travel

Residents rely on travelling

A cryoconite hole is a small pothole that forms in a glacier when some dark dust (“cryoconite”) absorbs the sun’s energy and melts the ice around it. You can see a diagram of this process here and photos of these holes here.

Some extreme organisms live in these cryoconite holes. They include bacteria, fungi, and microscopic ciliated protists, bdelloid rotifers, and the famous tardigrades (“water bears”). In order to thrive in the only occasionally hospitable puddles, these organisms must all regularly tolerate freezing, drying out, and being blown around to new holes. The cryoconite holes in Antarctica in particular are interesting ecosystems, as they will often keep a frozen ice lid even while melting out in the middle, isolating it from the atmosphere. What if they use up all their oxygen? Or all their carbon dioxide?

A few papers have been published on the residents of these cryoconite holes. A perhaps surprising amount of diversity exist in these holes for their extreme nature. I must have a little Took in me, because I am excited to travel to Antarctica myself to find out how this diversity of organisms persists. In the meantime, I am fortunate to have collaborators interested in finding out exactly who is living in samples they have brought back from previous work there.